Motion controller and synchronous control process therefor

ABSTRACT

In a system including a machine tool which operates on conveyed workpieces, a motion controller for the NC-controlled machine tool is improved by performing compensation for conveyor movement outside of the operation processor, so that compensation may be performed without modification of a machining program which does not take conveyor movement into consideration.

This is a divisional of application Ser. No. 07/723,116 filed Jun. 28,1991 pending.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a motion controller for controlling themachining of a workpiece traveling on a conveyor, in synchronizationwith the motion of the conveyor, and a synchronous control process forthat motion controller.

2. Description of the Background Art

A machining system which forms the environment for the present inventionis seen in FIG. 3 which is not prior art to the invention, where aconveyor 31 carries a workpiece 30 along a path in a direction D. Themovement of the conveyor is detected by an encoder 3, which generatespulses in response to the rotation of a conveyor roller or the movementof the conveyor itself past an internal sensor. A workpiece machiningposition is at a predetermined location along the path of conveyormovement and there is located before that position a sensor 32 fordetecting the presence of the workpiece. A machine tool (not shown) ismoved in horizontal and vertical directions by guides 33 and 34,respectively, each operating under control of a servo motor 15. Atypical servo-controlled structure using a ball screw for controllingmachine tool movement is seen in FIG. 10. The servomotor operates in aservo system that includes the motor 15, a position detector 16, servoamplifiers 14 and a motion control unit 1.

FIG. 7 is a block diagram illustrating a conventional motion controller.Referring to FIG. 7, the motion controller 1 includes an operationprocessor 2 for generating speed command data for a machine having atool that is movable to machine the workpiece. A synchronizing encoderis installed on a conveyor or similar transport mechanism and providesfeedback pulses to an encoder interface 4, which counts the feedbackpulses from the synchronizing encoder 3. A differential processor 5computes the number of pulses per unit time, based on an input from theencoder interface 4, and provides that quantity to the operationprocessor 2. External machine switches 6 are connected to an inputinterface 7 which provides corresponding signals to the operationprocessor 2. External lamps and indicators (e.g., a counter) 8, receivesignals from the operation processor 2 via an output interface 9. A CRToperation panel 10 is operative to interactively enter and modifyautomatic programs in a program file 11. Speed command data for each ofthe horizontal and vertical directions is output by the operationprocessor 2 in square pulse form and is converted into a smooth speedwaveform by an acceleration/deceleration processor 12, in order toreduce the mechanical shock which would be caused by attemptedinstantaneous compliance with the command pulse. The speed command dataoutput by the acceleration/deceleration processor 12 is accumulated by asumming device 13 and comprises position command data. The positioncommand data is input to a summing node 17 of a feedback servo controlloop, the node 17 providing a position deviation value to a servoamplifier 14. The servo amplifier output energizes a motor 15 fordriving the machine tool in a desired direction for machining theworkpiece. A detector 16 generates pulses in accordance with therotation of the motor 15 and provides the pulses to the summing node 17of the servo loop. Similar arrangements are provided for controllingboth the horizontal and vertical movement of the machine.

FIG. 8(a) provides a programming example for synchronous control usingconventional NC language, wherein G90 indicates use of absolutecoordinate values in program coordinates, G95 instructs a synchronousfeed mode, G01 defines linear interpolation, X and Y define orthogonaldirections and are followed by coordinate values of an end point, and Fdefines a feedrate per revolution of the synchronizing encoder 3, e.g.,"F10" specifies a feed of 10 mm per revolution. All of these programinputs must be specified by an operator.

Operation will now be described. When an automatic run mode selectsignal is entered by the corresponding machine switch 6 and an automaticrun₋₋ start signal is then entered, the operation processor 2 reads aprogram from the program file 11 and initiates an automatic run. Thecommand data provided at this time by the operation processor 2 iscreated in proportion to pulses fed back by the encoder 3. Hence, if theconveyor is stopped and there is no feedback pulse from the encoder 3,no command data is output by processor 2 and the motors 15 are alsostopped. When the conveyor moves, feedback pulses are generated by theencoder 3 and the command data is generated by processor 2.

The command data must be written in consideration of the movement of theconveyor in order to accurately move the machine tool to a target endpoint value on the conveyor, as shown in the programming example in FIG.8(a). For instance, assume that the encoder 3 rotates one turn while theconveyor moves 10 mm and the end point is reached when the conveyormoves 100 mm (the synchronizing encoder 3 rotates 10 turns). In FIGS.8(a) and 8(b) the Solid line arrows indicate the movement of the machinetool which would be required were the workpiece stationary, i.e., notconveyor mounted. The dotted line arrow indicates the actual tool pathnecessary to compensate for conveyor movement. In FIG. 8(a), the endpoint (X, Y) is nominally (-100, 0), however the end point changes to(-200, 0) when the movement of the conveyor is considered. The feedratealso changes from F10 to F20 when the movement of the conveyor isconsidered. The operator must therefore take account of the conveyorspeed and accordingly change the machining program.

In FIG. 8(b), where the end point (X, Y) is nominally (0,100), itchanges to (-100, 100) when the movement of the conveyor is considered.The feedrate per revolution of the encoder 3 at this time also changesfrom nominal F10 to F14.142 (=10×2 when the movement of the conveyor isconsidered.

As described above, the speed command data for each axis (X, Y) outputby the operation processor 2 is converted into a smooth command speedwaveform through the acceleration/deceleration processor 12 and isaccumulated at summing device 13 in order to create the position commanddata. The position command data is output to summing node 17 as thecommand data for a servo processor. The servo processor causes aposition loop to be formed using the position deviation value, servoamplifier 14, motor 15 and detector 16 so that the machine tool is movedto the commanded position.

FIGS. 9(a) and 9(b) illustrate the variation of conveyor speed (verticalaxis) with time (horizontal axis) beginning with a synchronization startsignal. The solid line in each Figure represents actual movement of themachine tool in the X direction, FIG. 9(b) having a higher conveyorspeed than FIG. 9(a). For a given conveyor speed, upon occurrence of thesynchronization signal, an acceleration/deceleration delay time constantof device 12 will "soften" the speed command and cause a slight delay inthe beginning of Command execution. The theoretical command line (i.e.,the theoretical machine tool speed, taking the delay time constant intoconsideration) is seen in FIGS. 9(a) and 9(b) as a dotted line, and isreferred to as the theoretical delay curve. However, due to inertia,processing time and the like, there will actually be some further delaybetween the issuance of the synchronization pulse, and time when themachine tool gets up to speed. The actual delay is seen as the solidline in the Figures and illustrates how the actual machine tool speedchanges with time, beginning with the occurrence of the synchronizationpulse, to eventually achieve a steady state at the desired speed. Aperiod of time will pass between the theoretical delay (dotted line) andthe actual movement of the machine tool (solid line). The product of thetime (sec) and the speed (mm/sec), i.e., the hatched area in theFigures, corresponds to the distance that the conveyor will move thework before the machine responds to the command. If this delay value isa constant, synchronization between the conveyor/workpiece and machinetool is readily achieved. However, as is evident from comparing FIGS.9(a) and 9(b), the delay value changes with different conveyor speeds.Thus, in the conventional art, the operator must conduct time runs todetermine what delay value should be used. As shown in FIGS. 9(a) and9(b), the delay value may be represented by the following expression andwill depend on the conveyor speed: ##EQU1## where, D=delay value (mm)

Fc=conveyor speed (mm/min.)

Ts=acceleration/deceleration time constant (sec)

Tp=position loop time constant (sec)

In the prior art, it was not possible to account for the delay timeother than through experimental test runs, thereby making operationdifficult and time consuming.

Another example of this type of controller is disclosed in JapanesePatent Disclosure No. 45887 of 1983. This system can establish speedsynchronization but similarly has the disadvantage in that the relativeposition of the tool and workpiece varies when the conveyorspeed-changes in real time. A process for controlling a robot insynchronization with a conveyor is disclosed in Japanese PatentDisclosure No. 67605 of 1989. That process operates on a target value bydetection of the movement of the conveyor by interpolation. However, theinterpolation period must be short in order to enhance the accuracy ofsynchronization.

The conventional motion controller and the synchronous control processtherefor as described above requires a machining program that operateson machining information, e.g., the moving speed, for machining aworkpiece on a conveyor, created in consideration of the moving speed ofthe conveyor. The variation of the motion delay value of the machiningdevice with respect to the moving speed of the conveyor makes itdifficult to synchronize the position of the conveyor with that of themachining device if the moving speed of the conveyor varies.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to overcome thedisadvantages in the prior art by providing a motion controller and asynchronous control process therefor which allow a machining program formachining a workpiece on a conveyor to be written without requiringconsideration of the moving speed of the conveyor.

A motion controller according to a first embodiment of the presentinvention comprises: machining information operating means for running amachining program for machining a workpiece on a conveyor via machiningmeans in accordance with an external command, operating on machininginformation on the workpiece, and outputting an operation result;conveyor movement information means for operating on movementinformation of the conveyor in accordance with a signal entered by anencoder for detecting the movement of the conveyor, and outputting anoperation result; and information combining means for combining conveyormovement information output by the conveyor movement informationoperating means with the workpiece machining information provided by themachining information operating means for machining the workpiece on theconveyor in synchronization with the motion of the conveyor.

In accordance with the first embodiment, the machining informationoperating means runs the machining program for machining the workpieceon the conveyor via the machining means in accordance with an externalcommand and operates on the machining information for the workpiece, andoutputs the operation result, the conveyor movement informationoperating means operates on the movement information on the conveyor inaccordance with the signal entered by the encoder for detecting themovement of the conveyor, and outputs the operation result, and theinformation combining means combines the conveyor movement informationoutput by the conveyor movement information operating means with theworkpiece machining information provided by the machining informationoperating means for machining the workpiece on the conveyor insynchronization with the motion of the conveyor.

In a motion controller according to a second embodiment of the presentinvention, the conveyor movement information operating means comprisesposition compensating means for maintaining a predetermined positionalrelationship of the machining means to the workpiece on the conveyor,independently of the magnitude of the conveyor moving speed.

In accordance with the second embodiment, the position compensatingmeans provided for the conveyor movement information means maintains apredetermined positional relationship of the machining means to theworkpiece on the conveyor, independently of the magnitude of conveyormoving speed.

A synchronous control process for a motion controller of the presentinvention comprises the steps of operating on movement information usingconveyor movement information from a signal entered by an encoder fordetecting the movement of the conveyor and outputting an operationresult; running a machining program for the machining of the workpieceusing machining information means in accordance with an externalcommand, operating on the machining information of the workpiece, andoutputting an operation result; and combining conveyor movementinformation output by conveyor movement information means with theworkpiece machining information provided by the machining informationmeans by using information over lapping means; and machining theworkpiece on the conveyor in synchronization with the motion of theconveyor.

In accordance with the method, the movement information of the conveyoris operated on and output by the conveyor movement information operatingmeans in accordance with the signal on conveyor movement entered by theencoder, the machining program for the machining means is run by themachining information means in accordance with the external commandentered, the machining information on the workpiece is operated on andoutput, and the conveyor movement information is overlapped with theworkpiece machining information by the information overlapping means tomachine the workpiece on the conveyor in synchronization with the motionof the conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a motioncontroller according to one embodiment of the present invention.

FIGS. 2(a) and 2(b) provide a program example for synchronous controlaccording to the present invention.

FIG. 3 is a synchronous control system configuration diagram.

FIG. 4 gives a program example for the execution of synchronous controlin the system shown in FIG. 3.

FIG. 5 is a compensation processing flowchart for the synchronouscontrol of position.

FIGS. 6(a), 6(b) and 6(c) illustrate a relationship between a conveyorspeed and a machine delay value during the execution of the processingshown in FIG. 5.

FIG. 7 is a block diagram illustrating the sequences of signals and datain the synchronous control of a motion controller known in the art.

FIGS. 8(a) and 8(b) give a program example for synchronous control inthe prior art.

FIGS. 9(a) and 9(b) provides a relationship between conveyor speed and amachine delay value in the prior art.

FIG. 10 is an illustration of a tool movement mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of the present invention will now be described withreference to FIGS. 1 to 6, wherein like reference characters designatelike or corresponding parts throughout the several views. The conveyorsystem employing the motion controller of the present invention wasdescribed above in connection with FIG. 3, and will be described furtherhere only as necessary for an understanding of the invention.

FIG. 1 is a block diagram showing the configuration of the motioncontroller 1A. Referring to FIG. 1, it should be noted that theoperation processor 2 does not receive any information concerningconveyor movement. The controller 1A includes a switching processor 21that is selectively operable to cause the performance of either a normalstate run in which the machine tool alone is controlled withoutconsideration of conveyor movement, i.e., when the conveyor is stoppedat a machining position (OFF), or the performance of a combined(machining/conveyor) run (ON). A combined run control signal 22 isoutput by the operation processor 2 and controls the state selected bythe switching processor 21. A unit conversion processor 23 receives theoutput of switching processor 21 and causes the conveyor velocityinformation from differential processor 5 to be converted into a unitsystem identical to that of a speed command. This unit conversion isaccomplished by an "electronic gearing" during a combinedmachining/conveyor run. A position compensating delay circuit 23A isoperative to set the delay between the detection of the workpiece andthe beginning of movement of the machine tool. This circuit will outputa value of 0 until the delay period has expired, at which point a speedcommand speed signal 24 is output by delay circuit 23A and is added tothe speed command pulse of the operation processor 2 at summing node 26.The delay value is dependent on the detected conveyor speed. The outputof node 26 is a combined speed command pulse that is softened byacceleration/deceleration device 12. The combined output is referred toherein as an "overlapping" signal or command that comprises acombination of regular machine command information and a correction forconveyor speed. The operation of circuit 23A in determining the delayvalue is presented in greater detail in FIG. 5 hereafter.

Alternatively, the output of position compensating 23A may be input to asecond summing junction 27, as a second speed command signal 25. Signal25 is identical to .the speed command signal 24, but in this case, isprovided after the output of the acceleration/deceleration processor 12.This improves the system's response to the conveyor as compared toaddition made at summing node 26 in front of theacceleration/deceleration processor 12. However, care must be takenbecause the mechanical system may be given a shock by a sudden change inspeed command for the mechanical system, when the command from theoperation processor 2 and the speed command signal from circuit 23A arecombined at node 27.

A conventional adder may serve as the combining circuit at node 26 or27. The machining information means comprises the operation processor 2,and the movement information means comprises the differential processor5, switching processor 21, unit conversion processor 23 and positioncompensating unit 23A.

FIGS. 2(a) and 2(b) show a programming example for this embodiment,wherein G90 defines absolute coordinate values as program coordinates,G94 specifies a feed mode per minute, G01 specifies linearinterpolation, X and Y followed by coordinate values define thecoordinates of an end point, and F defines a machine feedrate perminute, e.g., F1000 specifies a feed of 1000 mm per minute. Theeffective feedrate of the machine in the combined mode is the additionof the conveyor feedrate to F1000. As subsequently explained in greaterdetail, FIG. 2(a) illustrates the input of X coordinates, and theautomatic shift of program coordinates and FIG. 2(b) illustrates theinput of Y coordinates and the automatic shift. The important point isthat the program is here written without regard to the conveyormovement. That is, the programmer need not consider a moving frame ofreference when preparing a program, thus greatly simplifying theprogramming process. The conveyor speed is now taken into account bycircuit elements 21-27 (FIG. 1) automatically. Allowing the programmingto be free of speed conversion factors to accommodate conveyor speedalso allows programs previously written for a stationary workpiecesystem to be employed in a moving workpiece environment.

Referring again to FIG. 3, an embodiment of a machining system that maybe operated under synchronous control in accordance with the presentinvention is illustrated. A conveyor 31 is moved in the direction of thearrow and carries a workpiece to a position past a sensor 32, which isoperative to output a start signal. One driven axis 33 defines movementof the machining tool in a direction coincident with the feed of theconveyor 31 and performs position control in a horizontal direction. Asecond axis 34 defines movement of the machining tool and positioncontrol in a vertical direction.

FIG. 4 gives a sample program for synchronous control of a repetitivemachining process in the system configuration shown in FIG. 3. G53identifies a command to move the machine tool to a position specifiedwith respect to parameters (X,Y) in a machine coordinate system(intrinsic to the machine) here a position (X,Y)=(O,O); G0 identifies acommand for a rapid traverse; G92 is a command for presetting(initializing) the program coordinate system; and M10 is an auxiliarycommand in the NC language which will delay movement of the machineuntil the entry of an external signal, e.g., from the sensor 32 in thisexample. The program area from M10 to M11 performs an automaticmachining run that is coordinated with the feed of the conveyor. Duringthis period, the program coordinate system is automatically shifted inaccordance with the feed of the conveyor. M11 is an auxiliary commandlike M10 and is used as a command to end the combined run. M99 indicatesa return to the beginning of the program and re-execution of the sameprogram.

FIG. 5 is a flowchart illustrating the method of calculating theoverlapping movement per unit time with respect to the detected conveyorspeed. FIGS. 6(a) and 6(b) show delay values with respect to the motionof the conveyor when the processing in FIG. 5 is performed. As shown inFIGS. 6(a) and 6(b), the combining operation is conducted in order tomaintain a constant delay value as an operating parameter, even if theconveyor speed changes. The hatched area indicates a delay valueresulting from the acceleration/deceleration processor 12 during acommand smoothing operation (linear acceleration/deceleration) and theposition loop processing, etc. The delay value is proportional to theconveyor speed.

Operation of the system will now be described with respect to FIGS. 1,3, 4, 5 and 6(a) and 6(b). When an automatic run mode select signal isentered by the corresponding machine switch 6 and an automatic run startsignal subsequently is entered, the operation processor 2 reads amachining program from the program file 11, created beforehand throughthe CRT operation panel 10, and initiates an automatic run.

Referring now to the program in FIG. 4, when M10 is executed, themachine waits for a combined run start signal (from the sensor 32). Whenthe combined run start signal is entered, the operation processor 2outputs the combined run control signal 22, which then switches ON theswitching processor 21 to initiate a combined run operation. On start ofthe combined run operation, compensation is made to maintain theparameter-set delay value constant. The process for this purpose isshown in the flowchart of FIG. 5. In accordance with the program shownin FIG. 4, When M11 is executed, the operation processor 2 outputs acombined run end signal, which then switches OFF the switching processor21 to terminate the combined run operation.

The feedback pulses from the encoder 3 during the combined run aredifferentiated and then converted by the unit conversion processor 23into units that are identical to that of the speed command. The deliveryof the converted conveyor speed signals is then delayed in unit 23A, andthe signals are combined at summing junction 26 prior to theacceleration/deceleration processor 12 after a delay period that dependson the detected conveyor speed.

The overlapped movement per unit time may be calculated in accordancewith the flowchart illustrated in FIG. 5. The calculation is a functionof the current offset value (HOSEIA) and the theoretical offset value

(HOSEIB) for the distance traveled between the time that a workpiece isdetected by sensor 32 and the time that the machine, located at adownstream position, starts its operation. The theoretical offset iscalculated as follows: ##EQU2## where HOSEIB=theoretical offset value(mm)

SHIFT=parameter-set delay value with respect to the conveyor (constant).

Fc=conveyor movement per unit time (mm/ΔT)

ΔT=sampling period

Ts=linear acceleration/deceleration time constant (sec)

Tp=position loop time constant (sec)

By way of further explanation, the value "SHIFT" is a parameter valueset in advance within the system and is maintained equal to a constant.SHIFT corresponds to the sum of the hatched area and the white area(bounded by dotted lines) in FIGS. 6(a) and 6(b). HOSEIB corresponds tothe white area, while the area of the hatched region in FIGS. 6(a) and6(b) can be calculated from the right-hand term in equation (2) above.This term, referred to as "A", is dependent on the conveyor speed Fc andis thus not a constant. The term increases with increasing conveyorspeed because of the dependence on Fc, as can easily be seen from acomparison of FIG. 6(b) (high conveyor speed) and FIG. 6(a) (lowconveyor speed). Therefore, in order to maintain the value SHIFTconstant, the value HOSEIB must change with conveyor speed as well. Themanner in which HOSEIB is calculated is shown in FIG. 5; this algorithmis executed repetitively, at a rate on the order of 10 ms.

FIG. 6(c) illustrates a physical representation of SHIFT, HOSEIB, A, andB shown in FIGS. 6(a) and 6(b). As seen in FIG. 6(c), SHIFT representsthe distance between the detection point of the work (sensor 32), whichalso represents the point at which the synchronization start signal(overlapping command) is generated, and the location of the machine toolat its waiting point. HOSEIB represents the distance between thelocation of sensor 32 and the location of the work when the machine toolstarts to move. The value A corresponds to the distance between thelocation of the work when the machine tool starts to move and theinitial waiting point of the tool. Finally, value B is the distancebetween the initial tool waiting point and the location at whichworkpiece and tool are in synchronization registry.

As can be seen from the diagonal dotted lines in FIG. 6(c), the valuesof. HOSEIB, A and B are all variable with conveyor speed; only theparameter SHIFT is a constant.

Returning to the algorithm shown in FIG. 5, the process begins at stepS-50 by operator input of an initiate command. Calculation is started atstep S-50(a) and the encoder pulses are calculated at step S-50(b). Adetermination is made in step S-51 of whether an overlapping signalcommand has been input; if not, both the theoretical offset (HOSEIB) andcurrent offset (HOSEIA) values are set to zero and the overlapping valuedue to conveyor movement Fc' is set to zero in step S60 and this valueis added to the speed command of the operation processor at node 26 or27 with no effect. However, where there is an overlapping signal commandin step S-51, the process proceeds to use the synchronizing encoderpulse value calculated in step S-50(b) and a calculation of conveyormovement speed Fc is undertaken in step S-54. On the basis of thiscalculated value, the theoretical offset value is determined, usingequation (2), in step S-55. Then, in step S-56, a current offset valueis determined, using a previously determined value and the conveyormovement value Fc. A comparison of the offset values HOSEIA and HOSEIBas made in step S-57 and if HOSEIA is not greater than HOSEIB, theprocess proceeds to step S-60. However, if HOSEIA is greater, theprocess advances to step S-58 where the overlapping movement value (Fc')for conveyor movement compensation (Fc') is calculated. HOSEIA is thenset to HOSEIB, and the calculated value of Fc' is added to the speedcommand at step S-61. In other words, the overlapping movement value Fc'is zero until the current offset value (HOSEIA) exceeds the theoreticaloffset value (HOSEIB). At this point, the machine tool starts movingtoward the location where it will be speed-synchronized with theconveyed workpiece, as shown in FIG. 6(c). After overlapping is begun(Fc' is non-zero), the theoretical offset value (HOSEIB) is calculatedin real time in response to changes in the conveyor speed and theoverlapped movement is controlled to maintain a constant set delay value(SHIFT).

When it is necessary to improve the response to conveyor speed changes,input of the overlapping speed control signals may be performed at theoutput of the acceleration/deceleration processor 12 as indicated by theconnection of line 25 to node 27 in FIG. 1, instead of at the input tothe acceleration/deceleration processor 12 as described in the firstembodiment. In this case, the theoretical offset value HOSEIB in FIG. 5is represented by the following expression: ##EQU3## where,HOSEIB=theoretical offset value (mm)

SHIFT=delay value set in parameter (mm)

Fc=conveyor movement per unit time (ΔT)

ΔT=processing period

Tp=position loop time constant (sec)

Further, while the number of overlapping axes is limited to one in thedisclosed embodiment, a unit conversion processor 23 applicable to eachaxis may be used to allow overlapping for each axis, thereby allowingthe program coordinate system to be automatically shifted in more thanone axial direction.

It will be apparent, as described above, that according to theinvention, speed command overlapping circuitry combines conveyormovement information output by a conveyor movement detection unit withmachining information on the workpiece from the operation processor formachining the workpiece on the conveyor in synchronization with themotion of the conveyor. A position compensating means maintains apredetermined positional relationship between the machining device andthe workpiece on the conveyor, independently of the magnitude of themoving speed of the conveyor. A synchronous control process for a motioncontroller according to the invention includes a process of combiningthe conveyor movement information with the workpiece machininginformation and machining the workpiece on the conveyor insynchronization with the motion of the conveyor, so that the workpieceon the conveyor can be machined in synchronization with the motion ofthe conveyor without considering the feed of the conveyor in writing amachining program run by the machining information operating means.

What is claimed is:
 1. A motion controller comprising:machininginformation means for running a machining program to machine a workpieceon a conveyor via machining means in accordance with an externalcommand, operating on machining information on said workpiece, andoutputting an operation result; conveyor movement information means foroperating on movement information of said conveyor in accordance withdetected movement of said conveyor; and overlapping means foroverlapping conveyor movement information output by said conveyormovement information means with said workpiece machining informationprovided by said machining information means, for machining theworkpiece on said conveyor in synchronization with the motion of saidconveyor.
 2. A motion controller defined in claim 1, wherein theconveyor movement information means comprises position compensatingmeans for maintaining a predetermined positional relationship betweenthe machining means and the workpiece on said conveyor, independently ofthe magnitude of the moving speed of the conveyor.
 3. A synchronouscontrol process for a motion controller, comprising the stepsof:processing movement information on a conveyor using conveyor movementinformation entered by an encoder for detecting the movement of saidconveyor; running a machining program for a machine tool used formachining of a workpiece in accordance with an external command, andprocessing the machining information on said workpiece; and overlappingsaid processed conveyor movement information with said processedworkpiece machining information using information overlapping means andmachining the workpiece on said conveyor in synchronization with themotion of said conveyor.